Bootstrap 3 RTL Support

I have started working on adding RTL support to bootstrap 3.

I have done this by overriding the base styles for each component in a separate .less file, so it would be easier to integrate with the customizers.
I have also generated a separate .css file, rather than modifying "bootstrap.css" itself, because i think this is more in line with the way most themes and CMSs (drupal, wordpress, ...) handle multilingual sites.

The .html files have only been modified (through header-rtl.html) to include a link to bootstrap-rtl.css, and kept separate so that the original and rtl pages can be easily compared side-by-side.